During processing and/or testing of electronic devices, wafers often are transferred from one manufacturing device to another manufacturing device, such as in wafer cassettes. These wafer cassettes protect the wafers during transit and generally are configured to contain a plurality of wafers, with each wafer being located in a respective wafer slot within the cassette.
To complete a manufacturing operation on a given wafer, the wafer may be removed from the cassette and located within a manufacturing device. The wafer also may be moved from one location to another location within the manufacturing device. Wafer-handling end effectors may be utilized to remove the wafer from the cassette and/or to move the wafer within the manufacturing device. Historically, these end effectors are configured to contact a back, or bottom, side of the wafer, and the wafer is retained on the end effector via gravity and/or via a vacuum force.
As wafers become thinner, such as may be the case for wafers that are utilized during the manufacture of vertically oriented electronic devices (i.e., electronic devices that extend between a front side of the wafer and the back side of the wafer), the wafers may bow or otherwise deform or deflect to a non-planar orientation. This bowing may be the result of the gravitational force on the wafer and/or internal stresses within the wafer. To further complicate matters, this bowing may result in the wafer having a concave configuration, a convex configuration, a hyperbolic paraboloid configuration, or a mixture of concave regions and convex regions. Thin, bowed wafers present unique handling challenges, both in how to form a vacuum seal with the back side of the bowed wafer and in how to transfer the wafer without damage thereto. Thus, there exists a need for improved wafer-handling end effectors.